Supplies of helium – one of the world’s lightest gases – have been running short, prompting calls to ban it from leisure use in balloons so dwindling sources can be given over to scientific and medical use. Now, for the first time, a team has systematically tracked down a huge new reserve of the gas.

The reserve, discovered beneath the Great Rift Valley in Tanzania, is so large it could fill about 600,000 Olympic swimming pools.

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“No helium has been found deliberately before,” says Chris Ballentine of the University of Oxford, joint head of the team reporting the find this week at the Goldschmidt geochemistry conference in Yokohama, Japan. “This discovery makes it very likely that similar systems can be investigated and, where the geology works in the same way, more helium deposits will be found,” he says.

A million MRIs

Helium is used as a coolant in medical therapies and at the LHC, while NASA uses it in its rocket fuel. The gas has several other uses too – including novelty balloons – and supplies on Earth are dwindling. “At present day usage rates, all helium in known reserves will be used up by 2030 and 2040,” says Ballentine, whose find will buy us more time.

All helium on Earth is made from the decay of natural radioactive elements, such as uranium and thorium, which get trapped for hundreds of millions of years in ancient crustal rocks. Previous finds have come by chance.

Ballentine’s team found the new reserve in Tanzania’s Rukwa basin by following geological clues. “Just like an oil deposit, we looked for the helium equivalent of source rock, a mechanism by which it might get released, and a geological trapping structure,” says Ballentine.

The group searched there after working out that the Rift Valley’s volcanic activity could, over time, have provided enough heat to drive out helium caught in rocks, and trap it in underground caverns.

Jupiter calling

The team estimates that the reserve contains around 1.53 billion cubic metres – enough to fill 1.2 million MRI scanners, and seven times the amount of helium consumed annually.

“Before the invention of the MRI scanner, people couldn’t imagine what we’d need lots of helium for, and it was being disposed of cheaply,” says Tom Dolphin, a consultant anaesthetist in London and spokesman on the issue for the British Medical Association. “Who knows what amazing scientific advances will require a lot of helium in the future?” he says.

Despite the size of the new find, Dolphin warns against complacency. “Finding a new source of helium is great but it really only postpones the day when we run out,” he says. “The nearest ready supply of helium is on Jupiter, so while it’s great we have more for the time being, let’s not squander it.”